使paramiko库执行命令时，在给定的时间强制退出

 1 class SshClient(object):
 2 
 3     def __init__(self, ip, port, username, password):
 4         self.ip = ip
 5         self.host = host
 6         self.username = username
 7         self.password = password
 8 
 9     def exec_command(cmd, timeout):
10         log.info(u"在ip:%s上执行命令%s" % (self.ip, cmd))
11         sc = paramiko.SSHClient()
12         sc.set_missing_host_key_policy(paramiko.AutoAddPolicy())
13 
14         # 用来接收stdout stderror status信息
15         res = [None, None, None]
16 
17         def get_return(start_event,  res_list):
18             _, cmd_stdout, cmd_stderr = sc.exec_command(command=cmd, timeout=timeout)
19             channel = cmd_stdout.channel
20             cmd_status = channel.recv_exit_status()
21             res_list[0] = cmd_stdout
22             res_list[1] = cmd_stderr
23             res_list[2] = cmd_status
24             start_event.set()    # 表示线程已经执行完毕
25 
26         try:
27             sc.connect(hostname=self.ip, port=self.port, username=self.username, password=self.password, timeout=30)    # 这里的timeout是连接使用的，与我们要的不同
28             start_evt = Event()
29             t = Thread(target=get_return, args=(start_evt, res))
30             t.start()
31             start_evt.wait(timeout=timeout)
32             # 执行到这里说明线程已经退出
33             if None in res:
34                 raise Exception(u"命令超时退出")
35             stdout, stderr, status = res
36             if status != 0:
37                 raise Exception(u"命令执行返回非0！返回值为%s,错误信息为%s" % (status, stdout.read() + stderr.read()))
38             return stdout.read() + stderr.read()
39         finally:
40             sc.close()
41 }